The present invention pertains to an operatory stool of the type used by various branches of the medical arts and professions, such as dentists, ophthalmologists, and any other branch in which a medical professional or an assistant to said professional may be seated during professional operations. Such stools are mounted upon casters for ready mobility and the seat usually is vertically adjustable relative to base structure upon which the casters are mounted. At a location above the seat, a rest member is mounted upon one or more vertical post-like members which preferably are parallel to each other and the lower ends thereof are disposed in bearings supported by the seat. The rests may be of different shapes but, in general, are substantially arcuate and the same are upholstered to provide yieldability to a person occupying the seat and leaning against the rest for at least partial support thereby while performing professional operations.
To provide maximum comfort to a person occupying such stool, particularly in regard to leaning against said rest, it is customary to provide disengageable locking means operable to maintain the rest in a desired position of adjustment with respect to the seat, in either lateral or vertical directions. A typical example of such locking means is shown in U.S. Pat. No. 3,338,626, in the name of F. T. Hamilton, dated Aug. 29, 1967, and over which the present invention comprises an improvement.
For purposes of maintaining relative positions of arms or backs in various types of chairs, couches and the like, with respect to a seat, various types of releasable latch mechanisms have been employed, such as pivoted latch members having one end engageable with a series of notches disposed in an arcuate pattern. Examples of such adjusting means are shown in U.S. Pat. Nos. 247,350, dated Sept. 20, 1881, and 259,642, dated June 13, 1882, both in the name of Hofstatter, Jr.; and also in U.S. Pat. No. 1,334,365, dated Mar. 23, 1920, in the name of Freeman; and U.S. Pat. No. 1,663,864, dated Mar. 27, 1928, in the name of Russell.
Means for maintaining a pivoted back of a chair in various angular positions with respect to a seat and comprising a notched rod movable longitudinally in said seat and engageable by a spring-pressed pawl operated manually by a lever below the seat is illustrated in U.S. Pat. No. 879,489, dated Feb. 18, 1908, in the name of Pokorny.
For purposes of strength, durability, maintenance of desired adjusted positiones, notwithstanding the exertion of substantial physical forces against the rest of an operatory stool of the type to which the present invention pertains, as well as minimizing the possibility of repairs being required, the present invention has been devised, particularly to provide clutch mechanism of a different type from that shown in the aforementioned prior art, the details and advantages of which are set forth below.